The Canaries were 3-1 up at half-time but when the young Hornets pulled a goal back shortly after the break it seemed as though it was to be a repeat of Roots Hall on Tuesday night.
City striker Kris Renton had other ideas, making sure of all three points for the Canaries with a super strike six minutes from time.
City started the game on the back foot with Steve Arnold making a good save to deny Liam Henderson while Ewan Clarke blasted wide for the visitors after City were caught on the break.
With 18 minutes on the clock Watford opened the scoring when Lewis Young headed home from close range.
Rossi Jarvis gets to grip with his man
City goalscorer Chris Martin rises for a header
City had the perfect answer however just 60 seconds later when Renton sent in a low cross that saw Seb Muddel cleverly step over allowing Chris Martin to send in a low drive past James Beasant in the visitors goal.
Just five minutes later City took the lead when Aaron Beech put past his own keeper while under pressure from Renton.
It was looking good for the Canaries just three minutes later when they extended their lead after a good cross was met by Muddel who fired the ball into the far corner.
The visitors might have reduced the arrears shortly before the break when Alex Campana saw a shot come back off the upright.
Five minutes into the second half Watford did manage to pull a goal back after Arnold was bundled over allowing the ball to cross the line, amazingly referee Mr Ross signalling no foul.
Martin went even closer for City when he saw a 25-yard shot crash against the post but it was Renton who had the final say for City when he volleyed home from the edge of the box from a cross from substitute Gareth Matthews, who was making his first appearance for the Canaries.
City Line-Up: Arnold, Miller (Matthews 68), O'Toole, Lathrope, Quaye, Jarvis, Daley (Kelly 77), Muddel (Bexfield 68), Renton, Martin, Smart.
Subs not used: McLean, Byrne.
Top Canary: Luke Daley.
City celebrate Kris Renton's goal
